CERES-TRMM Table of Operations

Operations

February 24, 2000

It was decided after the eruption of the Mayung volcano on February 24 to power up the PFM instrument
about a week earlier than previously planned. Power up was initated at 21:32 UT on February 24, and all
aspects of the power on looked normal. The DAA+15-volt monitor showed a value of about 14.92 volts at
power up, but the output of the monitor began increasing and exceeded 20 volts within a few hours.
The instrument is expected to remain on during the remainder of the TRMM mission.

February 26, 2000

The CERES azimuth gimbal stalled after burn #1 of Delta-V #165 following the execution of the stored
command to send it from Contamination Safe to Crosstrack mode. Following burn #2 of Delta-V #165,
the instrument was commanded to the Safe mode at 18:36:22 UT. Instrument was commanded to cross-track
mode on Febrary 29 at 20:51:58 UT and remained in that mode while data were reviewed and evaluated
to help determine the cause of the stall anomaly.

February 27 - March 2, 2000

The CERES instrument Contamination Safe Mode azimuth angle was permanently redefined from 165° to
180° on Day 058 to match the Cross Track azimuth position and avoid the need to rotate in azimuth for
each maneuver.

CERES packets were commanded to gimbal type and AB asynchronous rotation
operations were performed on Day 059 (170° - 190°) and
Day 060 (160° - 200°) in an attempt to lubricate
the bearings and characterize their performance.
On Day 061, AB async operations continued using 150° - 210°.
The instrument stalled twice at 179.7° and 179.8° before being
commanded to Standby. Nominal Cross Track operations were then continued
at the 179.8° position, which is
essentially the nominal Cross Track position.

On Day 062, AB async testing was resumed (170° - 185°),
with stalls occurring again at 19:48 UT and 19:51 UT.
The range then changed to 175° - 185° and the instrument
successfully moved to 175° on command.
With that success, AB async testing was resumed
(160° - 200°) with no further stalls and
the instrument mode was commanded back to Cross Track at 22:26 UT.

AB Async Test Periods

Date

DOY

Time Period(UTC)

Duration(H:MM)

AB Range

2/28

059

17:47 - 17:59

0:12

170 - 190

2/29

060

13:44 - 13:57

0:13

160 - 200

3/1

061

20:50 - 20:53

0:03

150 - 210

3/2

062

20:48 - 22:24

1:36

Varied

March 6 - March 12, 2000

AB async testing continued this week, expanding the angles to 150° - 210°. Stalling still occurs
when traveling from Cross Track to angles greater than the 180° position (POSB), but is cleared when commanded
to angles less than 180° (POSA). During testing, SHORT elevation-scanning science data was collected for
approximately one orbit on Day 070. Testing will continue next week.

AB Async Test Periods

Date

DOY

Time Period(UTC)

Duration(H:MM)

AB Range

3/6

066

19:06 - 21:13

2:07

150 - 210

3/8

068

20:29 - 20:41

0:12

Varied

3/10

070

20:44 - 22:16

1:32

150 - 210

March 13 - March 19, 2000

AB async testing continued this week, expanding the angles to 150° - 210°. Stalling still occurs when
traveling from Cross Track to angles greater than the 180° position (POSB), but is cleared when commanded
to angles less than 180° (POSA).

AB Async Test Periods

Date

DOY

Time Period(UTC)

Duration(H:MM)

AB Range

3/13

073

18:47 - 20:58

2:11

Varied

March 20 - March 26, 2000

AB async testing continued this week, expanding the angles to 130° - 230°.

AB Async Test Periods

Date

DOY

Time Period(UTC)

Duration(H:MM)

AB Range

3/21

081

18:42 - 18:52

0:10

130 - 230

3/22

082

19:39 - 21:19

1:40

130 - 230

3/23

083

20:09 - 20:19

0:10

130 - 230

March 27 - April 2, 2000

AB async testing continued this week, expanding the angles to 90° - 270°.

AB Async Test Periods

Date

DOY

Time Period(UTC)

Duration(H:MM)

AB Range

3/27

087

19:34 - 21:42

2:08

90 - 270

3/28

088

20:33 - 20:44

0:11

90 - 270

3/29

089

17:43 - 19:16

1:33

90 - 270

3/30

090

15:51 - 16:02

0:11

90 - 270

April 10, 2000

The total channel thermal control was turned off.

April 18, 2000

The bridge balance window low, high and setpoint parameters in the stow
elevation scan profile were redefined, and a stow test performed to view
the noise level on the radiometric data.

April 19, 2000

A software patch was loaded which replaced the submux sampling of the +15V
DAA converter telemetry sampling with the +130V reading, and this diagnostic
provided no mitigration of the noise. All of the RAM (DAP and ICP)
memory was dumped to create a baseline map for future operations.

April 20, 2000

The Longwave channel thermal control was turned off and another stow test
was performed to view the bias on the data.

April 21, 2000

Solar presence sensors #1 and #2 were disabled at 12:02:16 and 12:03:04
respectively. The two sensors were enabled again at 17:23:22 and 17:23:55.
A patch was loaded to undo the +15V DAA-related patch that had been loaded
on April 19, ( See April 19 comment) and the Shortwave channel thermal
control was turned off. Short commands were sent to dwell the submux on,
first, a "quiet" analog telemetry point (MAM cover position), then on a
"noisy" telemetry point (Total channel monitor temperature). These
diagnostic tests clearly demonstrated that when the multiplexer dwells on a
single telemetry point the noise is completely removed from both science
and housekeeping telemetry. When the multiplexer was again cycled through
the lookup table, the noise returned. Finally, after the diagnostic tests
were completed, a software patch was loaded which provided a constant
heater power to the total channel sensor [as opposed to the nominal proportional
control algorithm] in order to get the sensor temperature back on scale.

April 24, 2000

The Total channel temperature controller was turned off at 12:06:52.
Solar presence sensors #1 and #2 were disabled at 20:26:08 and 20:27:08
respectively. The two sensors were enabled again at 21:51:45 and 21:52:22

April 26, 2000

A software patch was uploaded to the instrument which redistributes the sampling
pattern of the DAA submux over the analog telemetry points. The hypothesis that
maximizing dwell times on selected parameters and minimizing cycling among
parameters will reduce the magnitude of the noise to an acceptable level.

May 2000

The PFM instrument operated nominally in the cross-track scan mode, and
an internal calibration was performed on May 10.
Testing continued on two fronts: (1) To widen the range of azimuth drive
rotation capability - in preparation for future biaxial operations, and
(2) to test different software patches in an effort to reduce the noise
on the radiometric data channels.

AB Async Test Periods

Date

DOY

Time Period(UTC)

Duration(H:MM)

AB Range

5/18

139

18:43 - 18:50

0:07

90 - 270

5/22

143

18:46 - 18:58

0:08

90 - 270

5/31

152

19:01 - 19:12

0:11

90 - 270

May 19, 2000

Sensor coefficients were adjusted in an effort to reduce noise levels
resulting from operation of the temperature controllers.

May 22, 2000

Azimuth drive testing was performed and the sensor controller was turned
off for a short period of time.

June 2000

The PFM instrument experienced a major anomaly on June 14. After several
attempts to bring instrument back to normal operation, instrument was
commanded to safe mode on June 16 where it remained the rest of the
month. Heating may have been a contributing factor to the problem
because the orbit was approaching the point of maximum beta angle,
which is correlated with maximum solar heating. For more details about
anomaly, see comments for June 14, 15, and 16.

For the period of June prior to the anomaly, the PFM instrument operated
mostly in the cross-track scan mode. Testing of the azimuth drive
continued - to improve the capability to perform biaxial operation,
and various tests were performed to reduce the noise on the radiometric
detectors.

AB Async Test Periods

Date

DOY

Time Period(UTC)

Duration(H:MM)

AB Range

6/13

165

14:42 - 14:52

0:10

90 - 270

6/14

166

16:12 - 17:51

1:39

90 - 270

6/15

167

15:00 - 16:34

1:34

90 - 270

June 1, 2000

Microprocess patch loads were uplinked to redefine the function code and
calling functions for the three temperature controllers - Heatsink control
algorithm1.

June 14, 2000

At about 17:30 UT on June 14, output of the three CERES science channels began
displaying zeros. Simultaneously, the Data Acquisition Assembly housekeeping
parameters stopped updating, and most displayed values of zero.

June 15, 2000

Total, Window, and Shortwave controllers were turned off, and the DAP
and ICP control processors were reset, and no changes in the instrument
output or performances were observed. Initialization patch was reloaded
and the three controllers were turned off.

June 16, 2000

Instrument was commanded to safe mode where it remained for the rest of
the month of June.

August 15, 2000

There is a discrepancy in the times given for the Delta-V maneuvers. The TRMM Weekly
report states the times of the maneuvers as 15:32:16 UT and 16:18:02 UT, however; the Integrated
Print Report states the times of those maneuvers as 16:23:59 UT and 17:09:45 UT.

September 11, 2000

Patches were sent at 18:29 UT to reset the ICP processor.

September 17, 2000

The TRMM spaceraft experienced a power anomaly at 06:24:48 UT on
September 17 that resulted in commanding all instruments to their most
secure modes. All instruments except CERES were powered back on by
September 21. An initial investigation has led to the conclusion that the
spacecraft anomaly was the result of a false reading of the power status
indicator.

The CERES instrument was commanded to the survival mode when the
Spacecraft anomaly ocurred. Current plans call for returning the CERES
instrument to normal power-safe mode during the first week in October -
after values of the beta angle have passed through zero.

September 21, 2000

There is a discrepancy in the times given for the Delta-V maneuvers. The TRMM Weekly
report states the times of the maneuvers as 15:32:00 UT and 16:17:49 UT, however; the Integrated
Print Report states the times of those maneuvers as 15:41:18 UT and 16:26:57 UT.

September 22, 2000

On September 17 at 09:0050 UT, all instruments were powered off a
second time due to detection of a low battery charge state in PSIB-A
telemetry. It was determined that the PSIB-A telemetry can no longer be
used for reliable monitoring of the power system. A risk analysis was
performed and a decision was made to change the power management
configuration from Constant Current Mode with a cap of 12 amps per
battery to Peak Power Tracking with a VT-Level of 4. The CERES PFM
instrument has remained in the survival mode since the first power
anomaly on September 17. It is expected to remain in the survival mode
until around October 28 when values of beta angle pass through zero,
going from - to + values.

September 2000

All instruments were commanded to their secure modes
two times during the month, on September 17 and 22 - due
to detection of a spacecraft low power battery state. See
the expanded comments for September 17 and 22 for more
details.

Beta Angle - the angle between Sun vector and orbit plane calculated at noon Universal Time [UT].
Values are positive when the Sun is on left side of orbit, looking down range. Total
range of values for TRMM orbit is -58.5 to +58.5 degrees.

Calibration time in hours, and minutes, UT.

Internal calibrations with the blackbody and shortwave sources.

Solar calibrations with the Mirror Attenuator Mosaic at either sunrise or sunset.

Special operations such as the periodic yaw maneuver required to keep the Sun on the solar panels.